Pressure reduction valve

ABSTRACT

A pressure reduction valve for moving medium adapted to be connected into a conduit between the source of the pressure medium and a valve controlled tapping place. Between an inlet and an outlet is a device for executing a variable resistance against movement substantially dependent upon the pressure drop in the valve. The valve contains a run in a valve housing, one end of which is in connection with the outlet. An axially displaceable piston is arranged in the run, so that the piston will be subjected on its one side to the action of the inlet pressure and on its other side to the influence of the outlet pressure. The piston is under spring bias against the action of the inlet pressure and thereby tends to assume a position in which the action of the inlet pressure is equal to the action of the sum of the outlet pressure and the spring force. The valve contains a plurality of elongated relatively narrow by-pass-channels between the inlet and the outlet, which by-pass-channels are so shaped and arranged that they are opened or closed, respectively, dependent upon the position of the piston in the run, so that a progressively increasing number of by-pass-channels are opened and the effective resistance against movement of medium of the valve decreases when the piston is displaced in direction onto the outlet, and vice versa.

I Unlted States Patent 1 91 1 1 3,809,11 1 Olsson May 7, 1974 PRESSURE REDUCTION VALVE [76] Inventor: Anders E. I. Olsson, Frustunavagen [57] ABSTRACT 41 Alvsjo Sweden A pressure reduction valve for moving medium [22] Filed: July 7, 1971 adapted to be connected into a conduit between the source of the pressure medium and a valve controlled [21] Appl' 160335 tapping place. Between an inlet and an outlet is a device for executing a variable resistance against move- [30] Foreign Application Priority Data ment substantially dependent upon the pressure drop July 10, 1970 Sweden 9592/70 in the Valve The Valve contains a in a Valve h9hs- Mar. 23, 1971 Sweden 3727/71 8 9m end of which is in with the Outlet- An axially displaceable piston is arranged in the run, [52] US. Cl 137/503, 137/505.13, l37/516.13, so that the piston will be subjected on its one side to 13751615, 13751627 the action ofthe inlet pressure and on its other side to 51] Int. c1. Fl6k 17/04 the influence 0f the Outlet Pressure The Piston is 58 Field of Search..... 137/505.13, 516.27, 516.11, undet Spring bias against the action-9f the inlet p 137/53g 51 5 51 27 5 3 no 50 sure and thereby tends to assume a position in which 1 3 46 the action of the'inlet pressure is equal to the action of the sum of the outlet pressure and the spring force. [5 References Cited The valve contains a plurality of elongated relatively UNITED STATES PATENTS narrow by-pass-channels between the inlet and the 7 outlet, which by-pass-channels are so shaped and arigfs l ggg ranged that they are opened or closed, respectively, 2 918 082 12/1959 Garran.... 1 37 625.35 x dependent upon thePositifm of h piston in the 3:l38:l75 6/1964 Chilcoat 137/62537 x that a progressively increasmg number of 3,563,711 3/1971 Katz 137/516 pass-channels are opened and the effective resistance 3,093,155 6/1963 Dawes l37/516.1l x against movement of medium of the valve decreases 3,468,341 9/1969 Newcomb 137/505.13 X when the piston is displaced in direction onto the out- Primary Examiner-Harold W. Weakley Attorney, Agent, or Firm-Larson, Taylor & Hinds let, and vice versa.

10 Claims, 6 Drawing, Figures l l// I//// 1177 I 4 /y PRESSURE REDUCTION VALVE The present invention refers to such pressure reduction valves which are used both for reducing the presv sure in a feeder line, for instance to a tapping place provided with a control valve so that a suitable pressure is obtained at this tapping place, and for securing an even volume of medium stream. The invention has for its purpose essentially independently of the pressure in the feeder line to make sure a given limited maximum amount of streaming medium per unit of time to the consumption apparatus, which may in turn be controlled by the proper control valve of the consumption apparatus.

Different pressure reduction valves of similar kind are earlier known, all of which have had a variable movement resistance with a relatively small range of control, e.g., a local restriction of variable area. Such arrangements, however, have the disadvantage, especially if they should be installed in the piping to water consumption apparatus in dwelling-houses, that their sound level will be disturbingly high. This in turn depends upon that the range of pressure drop is limited to a short length with turbulent movement, and that the turbulent movement in turn will cause noice and rumbling, transplanting itself through the conduits.

One purpose of the present invention therefore is to remedy the noice and rumbling disturbances from a pressure reduction valve of the type mentioned above. The invention thereby is based upon the knowledge about that pressure reduction by laminar movement in channels with a relatively great length and small diameter will give an essentially smaller disturbing noice.

In order that one shall create the above mentioned maximum volume of moving medium per unit of time, independent of the feeder pressure, however, the valve arrangement must comprise means for variation of the movement resistance. It is technically difficult and unpractical to make this by variation of the length and/or the diameter of a channel for the moving medium, which would otherwise be able to give the desired result.

This invention instead is based upon that one should use a plurality of channels connectable in parallel to each other, similarily as a plurality of resistors connectable in parallel are used for controlling electric current.

In order to cause a correct control of the type intended, however, the parallel connection must take place as a function of the real drop of pressure over the resistances for the current medium and therefore be substantially independent of the feeder pressure, which corresponds to the relations in an electric constant current circuit. The invention therefore further is based upon the knowledge that a valve influenced by pressure from both sides, that means influenced on its one side by the input pressure and on its other side by the output pressure, and which is further biassed by a spring in a direction counter-acting the action of the input pressure, will at variation of any of the said pressure components displace itself in-axially direction to a position, dependent upon the difference in pressure, and that this displacement of position, which is thus substantially independent of the absolute valve of the input pressure may be used for adjustment of the resistance against moving medium.

The invention thus refers to an arrangement in pressure reduction valve for a medium moving under pressure and intended to be connected in the conduit between .the source of the medium under pressure and a valve controlled tapping place. The valve has an inlet and an outlet and is provided with means for execution of a variable resistance for the moving medium substantially independent of the pressure drop over the valve.

According to the inventionthe valve contains a run, arranged inside of a valve housing, one end of which being in connection with the inlet: to the valve and the other end being in connection with the outlet from the valve. A piston is arranged. axially displaceable in the run, so that the piston will be subjected on its one side for the action of the inlet pressure and on its other side be subjected to the action of the outlet pressure. The piston further is biassed by a spring against the action of the inlet pressure, so that it will always tend to assume a position, where the action of the inlet pressure is annulated by the action of the sum of the outlet pressure and the resilient spring pressure. The valve further contains a plurality of elongated rather narrow by pass-channels between the inlet and the outlet of the valve, which are so shaped and arranged that they are opened and closed dependent upon the position of the piston in the run, so that a progressively increasing number of by-pass-channels is opened and the effective resistance against movement of the valve decreases, when the valve is displaced in a direction onto the outlet and vice versa.

The invention will be further described below in connection with some forms of execution schematically shown in the attached drawings, but it is understood that the invention is not limited to these forms of execution, but that all different kinds of modifications may occur within the scope of the invention.

In the drawings FIG. 1 shows a longitudinal section through a valve according to the invention, and FIG. 2 is a cross-section through the valve according to FIG. 1 along the point dashed line in this Figure. FIG. 3 shows an electrical and logical circuit to the arrangement according to FIGS. 1 and 2. FIG. 4 shows a modification of the arrangement according to FIG. 1 and FIG. 2, in which the channels are arranged in the piston instead of, as in the arrangement according to FIGS. 1 and 2, in the valve housing. FIGS. 5 and 6 finally show a couple of more developed forms. of execution of the arrangement according to the invention.

The valve arrangement shown in FIGS. 1 and 2 contains a cylindrical valve housing 1 with inlet end 2 and outlet end 3. In the valve housing a cylindrical main passage or run 4 is arranged, which is in some suitable way at its one end connected to the inlet 2 and at its other end to the outlet 3. In the most simple form the run may in the way, shown in the drawing, be of uniform cross-section, but it is also understood that the valve should be capable of being attached to tubing and the like and that for this purpose the run and its connection means may require to be made with different diameters. In the cylindrical run 4 between its inlet and its outlet a cylindrical piston 5 is arranged, which is biassed by means of a pressure spring 6 in a direction onto the inlet 2. The spring in this case is introduced between a spring seat at the end of the piston 5 and a ring near the outlet 3 of the valve, but it may also act as a traction spring and be provided on the other side of the piston. The purpose of this spring 6 will be further described below.

Regarding initally only the said means in the valve, it is understood that the piston 5 is subjected on its end surface turned onto the inlet 2 to the inlet pressure P of the medium, for instance consumption water, the pressure of which is to be reduced by means of the valve. On the opposite end surface of the piston turned onto the outlet 3 the sum of the spring force F; and the outlet pressure P, will act. The change in this balance of pressure will cause an axial displacement of the piston in the run 2, which continues until balance has again been achieved between the existing pressures. This displacement is used according to the invention for connecting in or out, resp., the by-pass-ways between and the inlet andthe outlet of the valve. For this reason, the valve housing in the form of execution according to FIGS. 1 and 2 is provided with a number, e.g., three, of relatively narrow channels 7, 8, and 9 of substantially the same length but axially mutually displaced. The inlet opening of the channel 7 thus is situated closer to the inlet 2, the inlet opening of the channel 8 a little further displaced away in axial direction from said inlet, and most far into the valve is the inlet opening of the channel 9. The channels 7, 8 and 9 are in some suitable way distributed about the valve housing 1, preferably in a circular distribution with even distances.

As seen from the figures, the inlet openings of the channels 7, 8 and 9 are situated within a range, substantially corresponding to the axial length of the piston 5. In a given position of the piston 5 consequently all of the inlet openings of the channels are covered. The outlet openings of the said channels further are situated in a sufficiently great axial distance from the range of movement of the piston 5 in order that the piston when displaced against action of the spring 6 shall never cover any one of the outlet openings of the channels.

It is now evident that the invention is not limited to the use of only three channels. The greater the number of channels are and the narrower they are, the more even will the control he. Nor must the channels be completely contained in the material of the valve housing, but they may be formed by rifles having a suitable cross-section in the walls of the run. Finally they could be given a rather great length, which may take place by the channels starting in progressively increasing axial distances from the inlet 2 and continuing backwardly past the working range of the piston 5.

The valve according to the form of execution of this invention now described functions in the following way:

When the outlet is closed, for instance by the control valve in a subsequent consumption apparatus being shut off, an equalization of pressure will take place in the valve according to the invention, amongst others by leakage between the inlet and the outlet past the piston 5. It should be mentioned that in an arrangement according to the invention the tightening between piston and run may be rather bad without this influencing the proper functioning of the valve to any essential degree.

In certain cases, even the inlet end and the outlet end of the valve may be continuously connected over a suitable shunt conduit. Also this does not affect the function of the valve.

It should now be assumed that water or any other controlled medium is tapped on the outlet side of the valve. The pressure on the outlet side will then decrease, and the overweight of pressure on the inlet side tends to displace the piston 5 in a direction onto the outlet side or in other words to the right in the drawing. In the form of execution shown in FIGS. 1 and 2 the piston will then be displaced until it assumes the position indicated by dotted lines, which means that the inlet opening of the channel 7 is uncovered so that the medium, for instance water, may move through the channel 7 from its inlet to its outlet which is indicated by means of the dotted lines in FIG. 1. Dependent upon the characteristics and the bias of the spring 1 as well as on the pressure on the front side of the piston 5 and the pressure on the back side of the piston 5, this will stop its'displacement movement in a position where there is a balance, so that P, P, P,. Provided that the resistance against movement of medium through the consumption apparatus is not unnormally low or in other words that the medium pressure in the run at the outlet end P of the valve, which shall act on the backside of the piston, essentially approaches the difference between the inlet pressure P, and the total pressure drop in the channels, the valve according to the invention may serve for instance independently of the inlet pressure to limit the volume of movement on the outlet side to a predetermined maximum value. The spring 6 suitably is provided with a means not shown in the drawings for adjustment of the spring force dependent upon amongst other things the expected inlet pressure of the medium.

The function of the valve is schematically shown in FIG. 3, which shows an equivalent electrical wireing diagram over the valve arrangement according to FIGS. 1 and 2.

From the inlet conduit 2 the electrical current passes a switch 5' analogous to thepiston 5, which may connect the resistors 7', 8 and 9' step by step in parallel connection. The group of resistors is connected in series in the path of the current, so that the total resistance against current decreases step by step. The other ends of said resistors are connected to the output conductor 3'. One will nowfsee that the total resistance against current decreases at increasing inlet pressure P and that if the spring characteristic is chosen so that the spring force P, increases corresponding to the inlet pressure P these two magnitudes will be brought to compensate each other so that the outlet pressure P will be kept within wide limits at least approximately constant, independent upon the inlet pressure and independent upon the consumption on the outlet side of the valve.

In the arrangement according to FIG. 4 one may assume that this arrangement forms a kind of mirror image picture of the arrangement now described according to FIGS. 1 and 2, expressing itself in the channels being arranged in the piston, whereas instead the inner side of the cylindrical valve housing is smooth. Thus, one will find in the arrangement according to FIG. 4 the three channels 7", 8" and 9", which correspond as to their function to the already mentioned channels 7, 8 and 9, but which are arranged in the piston 5". The edge of the piston 5 in the arrangement according to FIGS. 1 and 2, serving to cover or uncover the openings to the channels 7, 8 and 9, correspond in the arrangement according to FIG. 4 to a recess on the inner side of the valve housing. Other means such as the spring 6 and so on in the arrangement according to FIGS. 1 and 2 correspond to similar means in the arrangement according to FIG. 4 and are carrying the same reference numerals along with a second sign.

The modifications and developments of the above described arrangements according to FIGS. 1 and 2 or FIG. 4, resp., which are shown in FIGS. 5 and 6, have for their purpose to make possible a more exact control, which should further within wide limits allow for the adaption of the control characteristic to the magnitude of the inlet pressure. The arrangements according to FIGS. 5 and 6 further allow for a control of the dynamic controlling properties of the valve, especially so that the reaction speed of the controlling means are limited and thereby also impact loads, so called water impacts are avoided. The constructions according to FIGS. 5 and 6 further will give the constructor a greater freedom when the question is one about providing a desired control characteristic in each separate case.

The valve shownin FIG. 5 is enclosed in a valve housing 1 1 which has been shown as an example in the form of a cylindrical sleeve. In the valve housing 11 thus there is a cylindrical run 12 which in the end of the arrangement according to FIG. 5 at right turns over into a somewhat wider cylindrical run 12. In the narrower part 12 of said run a ring-formed or cylindrically shellformed piston 13 is arranged in such a way that it will rather well tighten against the inner walls of the run 12. The ring-formed annular piston 13 is axially displaceable to and fro in the run 12. r

In the axial bore of the piston 13 a second cylindrical piston 14 is in turn axially displaceable.

The ring-formed piston 13 is supported by a spring 15 at its one end resting against a perforated disk 16, which is provided at its middle part with a hole corresponding to the cylindrical piston 14 so that this cylindrical piston 14 may pass freely through the hole. The disk 16 is kept in place between a recess in the turn over from the narrower piece 12 of the run to the wider piece 12' of said run, on the one hand, and a sleeve 17, on the other hand.

Hereby a space 18 is limited between the disk 16, the corresponding end of the ring-formed piston. 13, the outer mantle surface of the cylindrical piston 14 and the corresponding wall part of the run 12. The space 18 is in'connection with the outlet side of the valve over a narrow conduit 19, which may be controllable as'to its cross-section. The cylindrical piston 14 is supported over the prolongation 23 by a spring 24, resting on a disk 21, which is kept in place by its outer edge being spanned between the sleeve 17 and a further sleeve 22. The screw spring 24 thus contacts with its one end the outwardly directed flange on the prolongation 23 and with its other end the middle part of the disk 21. A bar 25 is attached to the disk 21, said bar extending into a corresponding hole in the piston 14 so that the spring 24 will get the required guiding in the sideward direction.

gated, rather narrow channels 29, 30 and 31, said number of channels in the form of execution according to In the cylindrical piston 14 there is a number of elonated outside of the circumference of the prolongation 23 of the piston.

The arrangement according to FIG. 5 functions in the following way: I

In the run at the left of the pistons a pressure medium is fed, usually a liquid, the pressure P of which should be reduced to a desired outlet pressure P For this pressure when medium is moving through the valve, then P will be less than P but when there is no movement of medium the two pressures are substantially equal. It is now understood that the ring-formed piston 13 will be subjected on its side turned onto the inlet to the pressure P which tends to displace the piston 13 to the right in FIG. 5. On the opposite side of said piston the sum of the pressure P, and the spring force from the spring 15, below indicated as P acts. The consequence will be, at least at low changes in the relation P /P that the ring-formed piston 13 tends to assume a position in axial. direction where the forces counter-acting each other are in balance, which means P P P By means of a controllable conduit 19 it is possible to cause the reaction of the piston for a momentary change of P or P to be damped, as far as the space inside of the disk 16 along with the amount of medium enclosed therein, usually an amount of liquid, will only move out from or into the space with a speed, which is determined in first place by the crosssection area of the controllable conduit 19. Itis then also understood that this arrangement dampens the acceleration of the movement of the ring-formed piston 13 in both directions.

The cylindrical piston 14 is axially movable substantially in the same way as already described in connection with the ring-formed piston 13. Thus, on the side of the piston 14 turned onto the inlet the pressure from the inlet medium P acts, which tends to displace the piston 14 at right in FIG. 5. On the opposite side of the piston 14 the sum of the pressure m and the force from the spring 24, here indicated as P acts. The piston 14 therefore tends to assume a balanced position, in which the two counteracting forces are substantially equal, which means P P P In the arrangement according to FIG. 5 the piston surfaces and the spring forces should be chosen in such a way that a change of the relation P,;,/P,,, will give a stronger reaction with the piston 13 than with the piston 14; in both cases the reaction is measured in the form of the displacement. The state shown in FIG. 5 thereby should correspond to the reaction for a great difference between P and P,,,, for instance caused by a consumption apparatus in which small resistance against movement of medium is. momentarily connected to the output side of a valve according to the invention. Before this took place, the two pistons thus were situated more far at left in the drawing Figure, so that the channels 29, 30, and 31 where covered with their months by the ring-formed piston 13.

As a chosen example for the function it is assumed that the ring-formed piston 13 is displaced a distance b at right as a reaction for a momentary decrease of the pressure on the output side of the arrangement, and that the reaction of the cylindrical piston 14 for same change of pressure is a displacement by the distance a in the same direction. Hereby, the openings to all of the three channels 29, 30 and 31 have been uncovered, which means that the resistance against movement of medium of the reduction valve has assumed its minimum value. If thereafter P rises, for instance if the consumption of medium on the output side decreases, the ring-formed piston 13 will move back a distance, for instance the distance b to the left in FIG. 5, so that perhaps one or more of the channel openings will again be covered. Thereby the resistance against moving medium is increased. It is then understood that the reduction valve according to FIG. 5 will in this way tend to adjust itself for a substantially constant output pressure, substantially independent of the input pressure.

The arrangement according to FIG. 6 differs from the arrangement according to FIG. 5 mainly in the following respects:

Whereas in the arrangement according to FIG. 5 the space 18 is in connection with the outlet side of the valve over a narrow conduit 19, the corresponding space 18 in the arrangement according to FIG. 6 is practically in unprevented connection with the outlet side of the valve through a plurality of openings 20 of a suitable form in the disk 16.

Whereas in the arrangement according to FIG. 5 the piston' 14 is supported against the one end of the screw spring 24, the other end of said spring being supported by the middle part of the disk 21, and a bar being arranged in the interior of the screw spring 24, the piston 14 is instead supported in the arrangement according to FIG. 6 against the end of a bellows 26, which is attached at its other end to the middle part of the disk 21. Over a conduit 27, which may be provided with a control arrangement 28, the interior of the bellows 26 is in connection with the surrounding atmosphere or perhaps with some source of a pressure medium, which is, however, not shown in the drawing, along with suitable sensing or indication means for the pressure in the interior of the bellows.

Whereas, in the arrangement according to FIG. 5 the existing openings through the disk screen 16 comprised narrow, valve controlled tubes 19, by means of which a damping of the movement of the pistons was obtained, greater holes 20 are arranged in the screen 16 in the arrangement according to FIG. 6. These do not give any damping, but the damping is nevertheless obtained in the arrangement according to FIG. 6, due to the action from the air existing in the interior of the bellows 26, which has to pass through the control arrangements 28 in the conduit 27.

For explanation of the function of the arrangement according to FIG. 6 one has in the equation of the equilibrium state to introduce the force from teh spring action of the bellows P instead of the force from the spring 24, P

Of course, if desired, one could use in one and the same valve both a spring 24 and a bellows 26.

By suitable choice of construction relations and dimensions one may adapt the control characteristics for a valve according to the present invention for a plurality of different purposes. One has thereby to take due regard to the mutual positions of the two pistons determining the resistance against movement of medium, whereas their positions in relation to the fixed parts of the valve, especially the valve housing, determines the spring bias and thereby also the magnitude in each separate point of the emanating reaction movement at a given change of pressure.

No exact mathematical analysis of the function is possible, in part because such analysis will give a differential equation, which is'in many a case not possible to solve by usual mathematics, in part because one does not know the characteristics of the springs in the form of mathematic formulas. An approximative analysis, however, can be made and this will then obtain the following form:

A change of the relation P /P will cause a displacement in one direction or the other one of the ring- .formed piston 13, so that the state of equilibrium is retained according to the equation (1) Analogically the change also causes a displacement in the one direction or the other one of the cylindrical piston 14, so that one will retain one of the following states of equilibrium, viz.

in ut 124 in ut na By suitable choice of the magnitude of the surfaces of the pistons and/or the spring forces one then arranges that for each deliberate change of pressure within the range of control of the valve the ring-formed piston will react with a greater axial displacement than the cylindrical piston.

In the equations 2A and 2B there is one factor missing, which dependent upon the execution of the construction in detail may have an essential influence on at least the dynamic but also on the static state in the valve, viz. the reaction force P, caused by the liquid moving out from the channels concerned. The direction of the force P, however is always counter-acting the force P This reaction force is not possible to calculate mathematically. Further it is to some extent dependent upon the properties of the consumption apparatus, and these, of course, are not known to the constructor of the valve.

I claim:

1. An automatically acting pressure reduction valve for controlling the pressure of a moving fluid medium between a pressurized area and a valve controlled tap for such medium in such a way that the pressure at the valve controlled tap will be at least approximately constant, comprising:

a housing having an inlet in fluid communication with the pressurized area, an outlet in fluid communication with the tap and at an outlet pressure, and a control means between said inlet and outlet for varying the resistance against movement of the fluid medium in response to the pressure drop across the pressure reduction valve, said control means including: an elongated main passage from said inlet to said outlet,

a piston positioned in said main passage for freely sliding axial movement therein, the upstream side of said piston being subjected to inlet pressure and the downstream side thereof being subjected to outlet pressure,

spring means for biassing the piston against the action of the inlet pressure,

- 9 the piston being freely movable to a position such that the force of the outlet pressure and the force of the spring equal the force of the inlet pressure,

selectively interconnect the said inlet and the said outlet for flow of the medium therethrough from said inlet to said outlet,-the outlets of the channels beingarranged such that the fluid flowing out of any given channel does not oppose the fluid flowing out of any other channel, said channels being arranged such that in response to movement of the piston from an initial position closest to the inlet in a direction towards the outlet as a result of an increase in the pressure drop across the piston, automatically a progressively increasing number of said channels are opened for the flow of the medium fluid therethrough from the inlet to the outlet. I 2. A pressure reduction valve according to claim 1, said channels being formed in the housing, the downstream side of said channels opening without obstruction into the outlet, the upstream ends of said channels being staggered in the direction of fluid flow and positioned such that all of them are normally covered by the piston at said initial position, these upstream ends successively being uncovered as the piston moves downstream as the pressure drop across the piston increases, thereby increasing the number of channels through which the fluid passes from the inlet to the outlet until an equilibrium is reached at which the force of the inlet pressure equals the force of the outlet pressure plus the spring force.

3. A pressure reduction valve according to claim 2, in which the channels are of substantially equal length and have the same cross-sectional area and are formed in theouter walls of the valve housing.

4. A pressure reduction valve according to claim 1, said spring means comprising an adjustable spring acting against one end of the piston.

5. A pressure reduction valve according to claim 1, said channels being formed in the piston, all of at least one of the said inlet or outlet ends being opened to the main passage, the other of said inlet or outlet ends being staggered, and said housing including a small cross-sectional area covering the staggered channel ends in said initial position of the piston, and said hous ing including an enlarged cross-sectional area adjacent the small cross-sectional area and positioned such that as the piston moves downstream in response to an increase in the pressure drop across the piston, said staggered channels are successively uncovered, thereby increasing the number of channels through which the fluid passes from the inlet to the outlet until an equilibrium is reached at which the force of the inlet pressure equals the force of the outlet pressure plus the spring force.

6. A pressure reduction valve according to claim 1, in which the piston is formed in two parts including a first piston which is annular in cross-section and a second piston movable in the interior of the first piston,

the annular piston being movable against the action of a first spring and provided in given positions to cover the said openings to the channels which are formed in the second interior piston, the latter piston being under the action of a second spring.

7. A pressure reduction valve according to claim 6, in which the first and second pistons are so dimensioned that the annular piston reacts more strongly to a change in the said pressure drop between the inlet and outlet than the interior piston.

8. A pressure reduction valve according to claim 6, in which at least one of said first and second pistons is provided with an acceleration damping means.

9. A pressure reduction valve according to claim 8,

in which the interior piston is displaceable through a screen arranged across the main passage, such that a pressure chamber which varies in volume upon displacement of the pistons will be formed between the side surface of the interior piston, the screen, the housing and the end surface of the annular piston, and including a choke channel arranged for releasing the pressure in said pressure chamber.

10. A pressure reduction valve according to claim 8, in which a bellows is provided between the downstream end of the interior piston and a screen extending across the main passage, said bellows being filled with a pressure receiving medium and said bellows being in fluid connection with the surroundings via a choke channel. 

1. An automatically acting pressure reduction valve for controlling the pressure of a moving fluid medium between a pressurized area and a valve controlled tap for such medium in such a way that the pressure at the valve controlled tap will be at least approximately constant, comprising: a housing having an inlet in fluid communication with the pressurized area, an outlet in fluid communication with the tap and at an outlet pressure, and a control means between said inlet and outlet for varying the resistance against movement of the fluid medium in response to the pressure drop across the pressure reduction valve, said control means including: an elongated main passage from said inlet to said outlet, a piston positioned in said main passage for freely sliding axial movement therein, the upstream side of said piston being subjected to inlet pressure and the downstream side thereof being subjected to outlet pressure, spring means for biassing the piston against the action of the inlet pressure, the piston being freely movable to a position such that the force of the outlet pressure and the force of the spring equal the force of the inlet pressure, a plurality of channels which are of sufficiently narrow crosssection compared with their length such that liquid flows through them with laminar movement, at least a major portion of each such channel extending in the direction of elongation of the main passage, said channels positioned to selectively interconnect the said inlet and the said outlet for flow of the medium therethrough from said inlet to said outlet, the outlets of the channels being arranged such that the fluid flowing out of any given channel does not oppose the fluid flowing out of any other channel, said channels being arranged such that in response to movement of the piston from an initial position closest to the inlet in a direction towards the outlet as a result of an increase in the pressure drop across the piston, automatically a progressively increasing number of said channels are opened for the flow of the medium fluid therethrough from the inlet to the outlet.
 2. A pressure reduction valve according to claim 1, said channels being formed in the housing, the downstream side of said channels opening without obstruction into the outlet, the upstream ends of said channels being staggered in the direction of fluid flow and positioned such that all of them are normally covered by the piston at said initial position, these upstream ends successively being uncovered as the piston moves downstream as the pressure drop across the piston increases, thereby increasing the number of channels through which the fluid passes from the inlet to the outlet until an equilibrium is reached at which the force of the inlet pressure equals the force of the outlet pressure plus the spring force.
 3. A pressure reduction valve according to claim 2, in which the channels are of substantially equal length and have the same cross-sectional area and are formed in the outer walls of the valve housing.
 4. A pressure reduction valve according to claim 1, said spring means comprising an adjustable spring acting against one end of the piston.
 5. A pressure reduction valve according to claim 1, said channels being forMed in the piston, all of at least one of the said inlet or outlet ends being opened to the main passage, the other of said inlet or outlet ends being staggered, and said housing including a small cross-sectional area covering the staggered channel ends in said initial position of the piston, and said housing including an enlarged cross-sectional area adjacent the small cross-sectional area and positioned such that as the piston moves downstream in response to an increase in the pressure drop across the piston, said staggered channels are successively uncovered, thereby increasing the number of channels through which the fluid passes from the inlet to the outlet until an equilibrium is reached at which the force of the inlet pressure equals the force of the outlet pressure plus the spring force.
 6. A pressure reduction valve according to claim 1, in which the piston is formed in two parts including a first piston which is annular in cross-section and a second piston movable in the interior of the first piston, the annular piston being movable against the action of a first spring and provided in given positions to cover the said openings to the channels which are formed in the second interior piston, the latter piston being under the action of a second spring.
 7. A pressure reduction valve according to claim 6, in which the first and second pistons are so dimensioned that the annular piston reacts more strongly to a change in the said pressure drop between the inlet and outlet than the interior piston.
 8. A pressure reduction valve according to claim 6, in which at least one of said first and second pistons is provided with an acceleration damping means.
 9. A pressure reduction valve according to claim 8, in which the interior piston is displaceable through a screen arranged across the main passage, such that a pressure chamber which varies in volume upon displacement of the pistons will be formed between the side surface of the interior piston, the screen, the housing and the end surface of the annular piston, and including a choke channel arranged for releasing the pressure in said pressure chamber.
 10. A pressure reduction valve according to claim 8, in which a bellows is provided between the downstream end of the interior piston and a screen extending across the main passage, said bellows being filled with a pressure receiving medium and said bellows being in fluid connection with the surroundings via a choke channel. 